Infrared sensor

ABSTRACT

An infrared sensor includes: an infrared detecting device; a lens disposed above the infrared detecting device; an member that is disposed at a side of an upper surface of the lens and includes an opening; and a gap that intervenes between the member and the lens and has a wider range than the opening.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication No. PCT/JP2012/079808, filed on Nov. 16, 2012, entitled“INFRARED SENSOR”, which claims priority based on Article 8 of PatentCooperation Treaty from prior Japanese Patent Application No.2011-273619, filed on Dec. 14, 2011, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to an infrared sensor.

BACKGROUND ART

Conventionally, there is known an infrared sensor that includes aninfrared detecting device, a package housing the infrared detectingdevice, and a semiconductor lens closing a window hole, in front of theinfrared detecting device, of the package (e.g., JP Pub. Nos.2011-220939 (Patent Document 1), 2007-292721 (Patent Document 2) and2010-237117 (Patent Document 3)).

In the infrared sensor, there is a concern about degradation indetection precision because an off-axis aberration occurs in a casewhere infrared (an off-axis light) emitted from an off-axis object pointis detected.

SUMMARY OF THE INVENTION

The present invention has been achieved in view of the abovecircumstances, and an object thereof is to provide an infrared sensorcapable of suppressing the occurrence of an off-axis aberration of anlens.

According to one aspect of the present invention, an infrared sensorincludes an infrared detecting device, a lens, a member and a gap. Thelens is disposed above the infrared detecting device. The member isdisposed on an upper surface of the lens, and includes an opening. Thegap is disposed between the member and the lens and has a wider rangethan the opening.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures depict one or more implementations in accordance with thepresent teaching, by way of example only, not bay way of limitations. Inthe figure, like reference numerals refer to the same or similarelements where:

FIG. 1 is a schematic sectional view of an infrared sensor in anembodiment;

FIG. 2A is a view illustrating propagation paths of infrared incident onthe infrared sensor in the embodiment, and FIG. 2B is a viewillustrating propagation paths of infrared incident on an infraredsensor in a comparative example;

FIG. 3 is a view illustrating another configuration example of a memberof the infrared sensor in the embodiment;

FIG. 4 is a schematic sectional view of an infrared sensor in anembodiment;

FIG. 5 is a schematic sectional view of an infrared sensor in anembodiment;

FIG. 6 is a schematic sectional view of an infrared sensor in anembodiment;

FIG. 7 is a schematic sectional view of an infrared sensor in anembodiment; and

FIG. 8 is a schematic sectional view of an infrared sensor in anembodiment.

DETAILED DESCRIPTION

Hereinafter, an infrared sensor in an embodiment is explained withreference to FIG. 1.

The infrared sensor includes an infrared detecting device 1, a package 3housing the infrared detecting device 1, and a lens 4 that is disposedso as to close a window hole 3 a, above the infrared detecting device 1,of the package 3. That is, in the infrared sensor, the package 3includes the window hole 3 a above the infrared detecting device 1, andthe lens 4 is disposed so as to close the window hole 3 a. The infraredsensor also includes: a member 5 that is disposed at a side of an uppersurface 4 a of the lens 4 and includes an opening 5 a defining aninfrared transmission region in the lens 4; and a spacer 6 thatintervenes between the member 5 and the lens 4.

The package 3 includes a package body 31 on which the infrared detectingdevice 1 is mounted, and a package lid 32 joined to the package body 31.The package lid 32 of the package 3 is formed with the aforementionedwindow hole 3 a. The lens 4 is joined to the package lid 32 through ajunction member 35. In the infrared sensor, the whole periphery of thelens 4 is joined to part, all around the window hole 3 a, of the packagelid 32. In the infrared sensor, an interior space (an airtight space)surrounded by the package 3 and the lens 4 is maintained under a drynitrogen atmosphere, but not limited to this. For example, it may bemaintained under a vacuum atmosphere. In a case where the interior spaceof the package 3 in the infrared sensor is maintained under a vacuumatmosphere, it is preferable that a getter for absorbing residual gasand the like within the package 3 be provided on an inside of thepackage lid 32. Preferably, material of the getter is, for example, anonevaporative getter of which activation temperature is about 300 to350° C. For example, a nonevaporative getter such as zirconium alloy,titanium alloy or the like may be employed.

The infrared sensor includes an IC device 2 configured to perform signalprocessing of an output signal from the infrared detecting device 1, andthe IC device 2 is also housed in the package 3. In the infrared sensor,the infrared detecting device 1 and the IC device 2 are arranged side byside in a lateral direction within the package 3. That is, the infrareddetecting device 1 and the IC device 2 in the infrared sensor arearranged side by side in the lateral direction on a first surface side(an upper surface side in FIG. 1) of the package body 31. However, thepackage 3 is not limited to the structure in which the IC device 2 andthe infrared detecting device 1 are housed therein side by side in thelateral direction. For example, the IC device 2 and the infrareddetecting device 1 may be housed in the package side by side in avertical direction.

In the package body 31, a wiring pattern (not shown) that electricallyconnects the infrared detecting device 1, the IC device 2 and the likeis formed on a substrate 31 a formed of insulating material. Respectivepads of the infrared detecting device 1 and the IC device 2 areconnected to the wiring pattern through wires (not shown). It is notnecessarily required that the IC device 2 is mounted with face up. Forexample, the IC device 2 may be mounted with face down. In this case,the pads of the IC device 2 can be connected to the wiring pattern withbumps. Also, in the infrared detecting device 1, by providingthrough-hole wirings for the infrared detecting device 1, thethrough-hole wirings may be connected to the wiring pattern throughbumps or the like. The package body 31 is formed with an electromagneticshielding layer 31 b, thereby functioning as an electromagnetic shield.On the other hand, the package lid 32 has electrical conductivity asdescribed later. The package lid 32 is electrically connected to theelectromagnetic shielding layer 31 b of the package body 31. The lens 4is made of silicon. Therefore, in the infrared sensor, theelectromagnetic shielding layer 31 b of the package body 31, the packagelid 32 and the lens 4 can have identical potential. As a result, theinfrared sensor has a function for shielding, from externalelectromagnetic noise, a sensor circuit (not shown) including theinfrared detecting device 1, the IC device 2, the wiring pattern and thelike.

In the infrared sensor of the embodiment, ceramics is employed as theinsulating material of the substrate 31 a of the package body 31.According to the infrared sensor, it is possible to improve moistureresistance and thermal resistance of the package body 31 in comparisonwith a case where organic material such as epoxy resin is employed asinsulating material. In the infrared sensor, if alumina is employed asthe ceramics of the insulating material, thermal conductivity of theinsulating material in the infrared sensor can be reduced in comparisonwith aluminum nitride, silicon carbide and the like. As a result, in theinfrared sensor, it is possible to suppress reduction in sensitivity ofthe infrared detecting device 1, caused by heat from the IC device 2 andan outside of the package 3.

In the package body 31, external connection electrodes 31 c electricallyconnected to the sensor circuit are formed from a second surface (alower surface in FIG. 1) to an outer periphery of the substrate 31 a.

The infrared detecting device 1 is joined to the package body 31 througha junction member 15 formed of a first die bond agent (e.g., siliconeresin). The IC device 2 is mounted on the package body 31 through ajunction member 25 formed of a second die bond agent (e.g., siliconeresin). Examples of each die bond agent include insulating adhesive suchas low-melting glass, epoxy resin and silicone resin, and conductiveadhesive such as solder (lead-free solder, gold-tin solder, etc.) andsilver paste. Alternatively, the infrared detecting device 1 and the ICdevice 2 may be joined to the package body 31 by, for example, roomtemperature bonding, or eutectic bonding with gold-tin eutectic, withoutusing the die bond agents.

In the package body 31, regions of the wiring pattern connected withground pads (not shown) of the infrared detecting device 1 and the ICdevice 2 are electrically connected to the electromagnetic shieldinglayer 31 b. Accordingly, in the infrared sensor, it is possible toreduce an influence of external electromagnetic noise onto the sensorcircuit formed of the infrared detecting device 1, the IC device 2 andthe like, and to reduce reduction in S/N ratio caused by the externalelectromagnetic noise.

The package lid 32 is, e.g., a metal cap shaped like a box with anopening at a face thereof on a side of the package body 31. The packagelid 32 is joined to the package body 31 so that the face of the packagelid is closed and sealed with the package body 31. The whole peripheryof the first surface of the package body 31 is formed with a metalpattern 31 d shaped like a frame along an outer periphery of thesubstrate 31 a in the package body 31. The package lid 32 and the metalpattern 31 d of the package body 31 are joined by metal junction of seamwelding (resistance welding process), thereby enhancing air tightnessand electromagnetic shield effect. The package lid 32 is made of Kovarand plated with nickel. The metal pattern 31 d of the package body 31 ismade of Kovar and plated with nickel and further plated with gold.

Joining of the package lid 32 and the metal pattern 31 d of the packagebody 31 may be other welding (e.g., spot welding) or joined byconductive resin, and is not limited to the seam welding. If aerotropicconductive adhesive is employed as conductive resin, it is possible tosuppress intrusion of external moisture and gas (e.g., moisture, oxygenand the like) into the package 3 because resin (binder) contains a lowcontent of conductive particles dispersed therein and a thickness ofjunction of the package lid 32 and the package body 31 can be thinned byapplying heat and pressure when joining them. Mixture containingdesiccant may be employed as the conductive resin. For example, bariumoxide, calcium oxide or the like can be employed as the desiccant.

Each outer periphery of the package body 31 and the package lid 32 isshaped like a rectangle, but not limited to the rectangle. For example,it may be shaped like a circle. The package lid 32 includes a brim 32 bprotruded outward from the whole periphery of end edges of the packagebody 31, and the whole periphery of the brim 32 b is joined to thepackage body 31.

The package body 31 may be formed of a printed wiring board which anelectromagnetic shield plate is embedded in. In this case, it ispreferable that a periphery of the package body 31 formed of the printedwiring board and the package lid 32 be joined and sealed with a junctionmember formed of conductive resin containing desiccant, B-stage epoxyresin having electrical conductivity or the like. For example, bariumoxide, calcium oxide or the like may be employed as the desiccant.

Each shape of the package body 31 and the package lid 32 in the package3 is not limited to the aforementioned examples. As an example of thepackage 3, the package body 31 may be shaped like a box having anopening at a first surface thereof (a rectangular box in this example),while the package lid 32 having the window hole 3 a may be shaped like aflat plate joined to the package body 31 so that the first surface ofthe package body 31 is closed and sealed. For example, the package 3 maybe a can package disclosed in Patent Document 2, but the structure ofthe can package is not limited to the structure of Patent Document 2.For example, in a case where the package 3 is the can package disclosedin Patent Document 2, a stem, a cap and a light transmitting windowdescribed in Patent Document 2 correspond to the package body 31,package lid 32 and the window hole, respectively.

An infrared sensor chip formed by a micromachining technique may beemployed as the infrared detecting device 1. For example, the infraredsensor chip may include a support substrate 1 a formed of asemiconductor substrate, and pixels 1 b (see FIG. 2A) arranged in array(e.g., two-dimensional array) on a first surface of the supportsubstrate, where each pixel includes a thermal infrared detector and aMOS transistor as a switching device for pixel selection. For example,an infrared array sensor disclosed in JP Pub. No. 2010-237117 may beemployed as the infrared sensor chip. In this infrared array sensor, atemperature sensing element of the thermal infrared detector is formedof a thermopile, and has a hot junction and a cold junction. In theinfrared sensor of the embodiment, it is preferable that the package 3is provided therein with a cover member 8 for equalizing temperaturechange values of a hot junction and a cold junction of each pixel 1 b inresponse to heat generation of the IC device 2. The cover member 8includes, above the infrared detecting device 1, an opening window 8 athat allows infrared toward the infrared detecting device 1 to passtherethrough. An outer periphery of the infrared detecting device 1 isshaped like a rectangle, and the opening window 8 a is an opening shapedlike a rectangle. The opening of the opening window 8 a is shaped so asto be a similar figure to the outer periphery of the infrared detectingdevice 1, but is not necessarily a similar figure.

Material of the cover member 8 is Kovar, but not limited to this. Forexample, stainless steel, copper, aluminum or the like may be employed.

The cover member 8 is joined to the package body 31 through a junctionmember 9. Examples of material of the junction member 9 includeelectrically conductive paste (e.g., silver paste and the like), epoxyresin and the like.

In the infrared sensor of the embodiment, the cover member 8 is providedin the package 3 and it is accordingly possible to equalize heat topropagate toward the pixels 1B because heat caused by heat generation ofthe IC device 2 is to propagate toward the pixels 1B of the infraredsensor chip as the infrared detecting device 1 by way of a path passingthrough the package body 31 and a path passing through the cover member8. As a result, the infrared detecting device can suppress thedispersion of offset voltages in a surface of the infrared sensor chipcaused by heat generation of the IC device 2 and suppress the dispersionof S/N ratio. In the infrared sensor, it is therefore possible to reducea difference between an offset voltage of a temperature sensing elementin each pixel 1 b (a pixel 1 b on left end of FIG. 2A) of the infraredsensor chip, nearest to the IC device 2 and an offset voltage of atemperature sensing element in each pixel 1 b (a pixel 1 b on right endof FIG. 2A) farthest from the IC device 2.

Since the cover member 8 is provided in the package 3, the infraredsensor can prevent infrared radiation from the IC device 2 caused byheat generation of the IC device 2 and infrared radiation from thepackage lid 32 from directly reaching the infrared detecting device 1.

The infrared sensor chip as the infrared detecting device 1 is notlimited to the structure disclosed in the aforementioned document. Itmay have a configuration that thermal infrared detectors are arranged inarray on the first surface side of the support substrate 1 a. Atemperature sensing element of each thermal infrared detector is formedof a thermopile, but not limited to the thermopile. It may be formed of,for example, a resistance bolometer, a pyroelectric thin film or thelike. In a case where each temperature sensing element of the infraredsensor chip as the infrared detecting device 1 is formed of athermopile, it is preferable that the infrared sensor be configured sothat a thermistor for measuring an absolute temperature is also housedin the package 3.

In the infrared sensor chip as the infrared detecting device 1, a MOStransistor is provided for each pixel 1 b, but is not necessarilyprovided. In addition, the infrared detecting device 1 may include atleast one temperature sensing element, and is not necessarily theinfrared sensor chip including the pixels 1 b arranged in array. Theinfrared detecting device 1 may be pyroelectric element formed of apyroelectric substrate. In this case, in secondary mounting of theinfrared sensor on a circuit board such as a printed wiring board or thelike, it is preferable to employ lithium tantalate (LiTaO₃) or lithiumniobate (LiNbO₃) of each of which Curie temperature is higher than thatof lead zirconate titanate (Pb(Zr,Ti)O₃:PZT) as material of apyroelectric element in consideration with the usage of lead-free solder(e.g., SnCuAg solder or the like) as joining material. Examples of thepyroelectric element include a quad type element in which four elements(a light receiving element) are formed on a single pyroelectricsubstrate in two-by-two or linear array, a dual type element in whichtwo elements are formed thereon in linear array, and the like. It isaccordingly possible to reduce output fluctuation of the pyroelectricelement, caused by heat from an outside. The pyroelectric element is notlimited to the quad type element and the dual type element. For example,a single type element may be employed.

The IC device 2 is an ASIC (Application Specific IC) and includes asilicon substrate. The IC device 2 is not limited to the ASIC. An ICincluding specified integrated signal processing circuit may beemployed. A bare chip is also employed as the IC device 2. Therefore, inthe infrared sensor of the embodiment, the package 3 can be miniaturizedin comparison with an IC device 2 formed by packaging a bare chip.

Preferably, the circuit of the IC device 2 is appropriately designed inresponse to a kind of the infrared detecting device 1. For example, in acase where the infrared detecting device 1 is the aforementionedinfrared sensor chip, the circuit may be configured to include a controlcircuit configured to control the infrared detecting device 1, anamplifier circuit configured to amplify an output voltage of theinfrared detecting device 1, and a multiplexer configured toalternatively provide the amplifier circuit with output voltages ofinput pads electrically connected to output pads of the infrareddetecting device 1. According to the circuit, an infrared image can beobtained. In this example, the IC device 2 includes an arithmeticcircuit configured to obtain a temperature based on an output of theamplifier circuit (an output in response to a difference in temperaturebetween a hot junction and a cold junction of a pixel 1 b) and an outputof the thermistor (an output in response to an absolute temperature,which is regarded as an output in response to a temperature of a coldjunction of a pixel 1 b). In the device, an infrared image can bedisplayed on an external display. In a case where the infrared sensorfunctions as a human sensor and includes the aforementioned pyroelectricelement as the infrared detecting device 1, a circuit of the IC device 2may be configured to include a current/voltage conversion circuitconfigured to convert a pyroelectric current as an output signal fromthe infrared detecting device 1 into a voltage signal, a voltageamplifying circuit (a band pass amplifier) configured to amplify avoltage signal having a specified frequency band of a voltage signalfrom the current/voltage conversion circuit, a detection circuitconfigured to compare the voltage signal from the voltage amplifyingcircuit with a specified threshold to output a detection signal when thevoltage signal exceeds the threshold, and an output circuit configuredto output the detection signal of the detection circuit as a human bodydetection signal.

Infrared assumed in the infrared sensor of the embodiment contains awavelength range (8 μm to 13 μm) around 10 μm radiated from a human bodyas the infrared that is a detection target of the infrared detectingdevice 1. Accordingly, silicon is employed as material of the lens 4.However, the material of the lens 4 is not limited to silicon. Forexample, germanium, zinc sulfide, gallium arsenide or the like may beemployed. Preferably, silicon is employed because it provides a lowenvironmental load in comparison with zinc sulfide, gallium arsenide andthe like, reduction in cost in comparison with germanium, and lowwavelength dispersion in comparison with zinc sulfide. A wavelengthrange or a wavelength of the infrared as the detection target is notlimited to the aforementioned wavelength range. It may be appropriatelyset according to the practical use of the infrared sensor (e.g., the useof human detection, the use of gas detection or flame detection, or thelike).

It is preferable that an optical filter film be provided on at least oneof a side of the upper surface (an incoming surface for infrared) 4 aand a side of a lower surface (an outgoing surface for infrared) 4 b ofthe lens 4. Preferably, an optical property of the optical filter film(a filter property) is set based on a wavelength range or a wavelengthof the infrared as the detection target by the infrared detecting device1.

In the infrared sensor of the embodiment, a wavelength range of theinfrared assumed as the detection target is 8 μm to 13 μm, and theoptical property of the optical filter film is optically designed sothat the infrared having a wavelength range of 5 μm to 15 μm passestherethrough. However, it is preferable that the optical design beappropriately performed in response to a wavelength range or awavelength of the infrared as the detection target according to thepractical use of the infrared sensor.

For example, the optical filter film may be formed by alternatelystacking thin films of which refractive indexes are different from eachother. Examples of material of each thin film include germanium, zincsulfide, selenium sulfide, alumina, silicon oxide, silicon nitride,magnesium fluoride and the like.

In the infrared sensor, the lens 4 is appropriately provided with theoptical filter film, thereby enabling removal of a visible light and aninfrared light in an unnecessary range other than a specified wavelengthregion and the suppression of an occurrence of noise caused by sunlightand the like. It is accordingly possible to enhance the sensitivity.

In a case where the optical filter film is provided for each side of theupper surface 4 a and the lower surface 4 b of the lens 4, opticalproperties of the two optical filter films may be the same as ordifferent from each other. For example, the lens 4 may be opticallydesigned so that the optical filter film on the side of the uppersurface 4 a removes infrared of 2 μm to 5 μm and the optical filter filmon the side of the lower surface 4 b removes infrared of 2 μm or less.The lens 4 may be configured so that one of the side of the uppersurface 4 a and the side of the lower surface 4 b is provided with theoptical filter film and the other is provided with an antireflectionfilm for preventing infrared reflection. The antireflection film may beappropriately designed to have laminate structure by using materialsimilar to the optical filter film.

An optical film of the aforementioned optical filter film or theantireflection film may be formed by forming a film by using a thin filmforming technology such as an evaporation method or a sputtering methodto then apply patterning by using a photolithography technique and anetching technique or patterning by a laser beam or patterning by using adicing saw. When forming the optical film by using the thin film formingtechnology such as the evaporation method or the sputtering method, theoptical film may be formed only in a specified region by arranging anappropriate shadow mask. As a result, it is possible to omit apatterning process for the optical film after forming the optical film.

For example, solder or the like may be employed as material of thejunction member 35 that joins the lens 4 and the package lid 32. In acase where solder is employed as the material of the junction member 35,it is preferable that a metallization film (a metal film) made ofmetallic material having good wettability with the solder at a region,corresponding to the junction member 35, of the lens 4. For example, thejunction member 35 may be formed of a first region made of low-meltingglass and a second region made of electrically conductive paste.Preferably, lead-free low-melting glass may be employed as theaforementioned low-melting glass. Silver paste is employed as theelectrically conductive paste, but is not limited to this. Theelectrically conductive paste is formed of conductive filler and binder.Examples of the conductive filler include silver, gold, copper, nickel,aluminum, carbon, graphite and the like. Examples of the binder includeepoxy resin, urethane, silicone, acrylic, polyimide and the like. In acase where the junction member 35 of the infrared sensor is formed ofthe first region and the second region, if low-melting glass is used formaterial of the first region inside the second region, it is possible todecrease outgas within the package 3 from the junction member 35 and toprevent deterioration in characteristics and reduction in productionyield caused by the outgas.

Preferably, aspherical lens like plano-convex lens is employed as thelens 4. In an arrangement of the infrared sensor of the embodiment, afirst surface, shaped like a plane, of the lens 4 is the upper surface 4a, and a second surface, shaped like a convex surface, of the lens 4 isthe lower surface 4 b. In the infrared sensor of the embodiment, adetection area of the infrared detecting device 1 can be set by the lens4 and the member 5.

Preferably, the lens 4 is formed of a semiconductor lens (e.g., asilicon lens or the like). In a manufacturing example of thesemiconductor lens, a semiconductor substrate (e.g., a silicon substrateor the like) is prepared. An anode by designing a contact pattern withthe semiconductor substrate in accordance with a shape of a desired lensis then formed on a first surface side of the semiconductor substrate soas to form ohmic contact as contact with the semiconductor substrate. Asecond surface side of the semiconductor substrate is anodized in anelectrolytic solution containing a solution for removing, by etching,oxide of constituent element of the semiconductor substrate, therebyforming a porous region to be removed. The porous region is thenremoved, so that a semiconductor lens is formed. For example, productionmethods for semiconductor lens disclosed in JP Pub. Nos. 3897055,3897056 and the like can be applied as the above sort of productionmethod for semiconductor lens based on anodic oxidation technology. Inthe lens 4 formed of the aforementioned semiconductor lens, it ispreferable that numerous lenses 4 be formed by employing a semiconductorwafer (e.g., a silicon wafer) as the semiconductor substrate and thenseparated individually by dicing or the like.

In the infrared sensor of the embodiment, an aspherical lens formed ofthe semiconductor lens is employed as the lens 4, and it is accordinglypossible to obtain small aberration in comparison with a spherical lensformed by cutting work even in a lens 4 that has a short focus and alarge opening size. Thus, the focus is shortened, and thereby thepackage 3 can be thinned. In the infrared sensor of the embodiment, thesecond surface, shaped like the convex surface, of the lens 4 isdisposed at a side of the window hole 3 a of the package lid 32 and partof the lens 4 can be housed in the window hole 3 a. As a result, thepackage 3 can be further thinned.

Preferably, the lens 4 is a semiconductor lens integrally formed of alens portion 41 and a flange portion 42 surrounding the whole peripheryof the lens portion 41. As a result, in the infrared sensor, the spacer6 interposed between the lens 4 and the member 5 can be interposedbetween the flange portion 42 of the lens 4 and a periphery of theopening 5 a in the member 5. Therefore, in the infrared sensor, it ispossible to enhance parallelism of the member 5 with respect to thefirst surface of the lens 4 and to improve optical-axis alignmentbetween the member 5 and the lens 4. The infrared sensor includes theflange portion 42 which has a constant thickness, and each face of theflange portion 42 on both sides of a thickness direction is shaped likea plane. As a result, it is possible to enhance precision of a distancebetween the lens 4 and the infrared detecting device 1 in an opticalaxis direction of the lens 4.

The lens 4 may include a level difference which is formed along thewhole periphery of the flange portion 42 and positioned at part, aroundthe window hole 3 a, of the package lid 32 and an inside of the windowhole 3 a. In this case, it is preferable that the level difference ofthe lens 4 is joined to part, all around the window hole 3 a, of thepackage lid 32 through the junction member 35. Thus, if the leveldifference is provided, it is possible to enhance parallelism betweenthe lens 4 and the infrared detecting device 1, and precision of thedistance between the lens 4 and the infrared detecting device 1 in theoptical axis direction of the lens 4. For example, the level differencemay be formed by using a dicing blade or the like at a stage of thesilicon wafer before separation, or formed by a photolithographytechnique or an etching technique before a dicing process.

An outer periphery of the member 5 is shaped like a rectangle that isthe same as an outer periphery of the lens 4. The opening 5 a of themember 5 is shaped like a circle. The opening 5 a of the member 5 has aninternal diameter that is set smaller than a lens diameter of the lens4. It is preferable that the member 5 is disposed so that the opticalaxis of the member 5 agrees with the optical axis of the lens 4.

Examples of material of the member 5 include silicon, glass and thelike. In a case where silicon or glass is employed as the material ofthe member 5, the member 5 may include a metal film or the like as alight shielding film for shielding infrared at an opposite side of amember substrate from the lens 4, where the member substrate is formedof silicon, glass or the like. Examples of material of the metal filminclude gold, chromium, nickel, titanium and the like. The metal filmmay be formed by forming a film by using a thin film forming technologysuch as an evaporation method or a sputtering method to then applypatterning by using a photolithography technique and an etchingtechnique. When forming the metal film by using the thin film formingtechnology such as the evaporation method or the sputtering method, themetal film may be formed only in a specified region by arranging anappropriate shadow mask. As a result, it is possible to omit apatterning process for the metal film after forming the metal film.

In a formation process of the member 5, numerous members 5 may be formedon a wafer (hereinafter called a first wafer) formed of silicon, glassor the like and then separated individually by dicing or the like. In acase where silicon is employed as material of the first wafer, theopening 5 a of the member 5 may be formed by, for example, etching suchas wet etching in which an alkali solution that is a TMAH (tetra-methylammonium hydroxide) solution or the like is used, or dry etching inwhich dry etching apparatus that is a type of inductively coupled plasmaor the like is used. In a case where an area of the opening 5 a of themember 5 is constant regardless of a distance from the lens 4, by usinga silicon wafer with a main surface of (110) plane as the first wafer,it is possible to form the opening 5 a even by the wet etching in whichthe alkali solution is used. The dry etching apparatus is not limited tothe type of inductively coupled plasma. It may be a dry etchingapparatus which has a comparatively high etching rate with respect tothe first wafer and of which control of an opening shape of the opening5 a is comparatively simple. In a case where glass is employed as thematerial of the first wafer, the opening 5 a of the member 5 may beformed by, for example, blast processing or the like.

Examples of material of the spacer 6 include silicon, glass and thelike.

The spacer 6 is shaped like a frame. In the embodiment, an outerperiphery of the spacer 6 in planar view is shaped like a rectangle thatis the same as the outer periphery of the lens 4, and an inner peripherythereof in planar view is shaped like a circle that is larger ininternal diameter than an inside of the opening 5 a of the member 5. Asa result, the infrared sensor of the embodiment includes a gap 7 thatintervenes between the member 5 and the lens 4 and is formed in a widerrange than the opening 5 a of the member 5. In the infrared sensor ofthe embodiment, the gap 7 is formed of a hollow space that is shapedlike a cylinder and surrounded by the member 5, the lens 4 and thespacer 6.

In a formation process of the spacer 6, it is preferable that numerousspacers 6 may be formed on a wafer (hereinafter called a second wafer)formed of silicon or glass and then separated into individual spacers 6by dicing or the like. In a case where silicon is employed as materialof the second wafer, the opening 6 a of the spacer 6 may be formed by,for example, etching such as wet etching in which an alkali solutionthat is a TMAH solution or the like is used, or dry etching in which dryetching apparatus that is a type of inductively coupled plasma or thelike is used. In a case where an area of the opening 6 a of the spacer 6is constant regardless of a distance from the lens 4, by using a siliconwafer with a main surface of (110) plane as the second wafer, it ispossible to form the opening 6 a even by the wet etching in which thealkali solution is used. The dry etching apparatus is not limited to thetype of inductively coupled plasma. It may be a dry etching apparatuswhich has a comparatively high etching rate with respect to the secondwafer and of which control of an opening shape of the opening 6 a iscomparatively simple. In a case where glass is employed as the materialof the second wafer, the opening 6 a of the spacer 6 may be formed by,for example, blast processing or the like.

Preferably, individual optical members each of which integrally includesthe spacer 6, lens 4 and the member 5 are obtained by dicing wafer-levelstructure in which the second wafer, the semiconductor wafer and thefirst wafer are joined at wafer-level so that each spacer 6 is joined tocorresponding lens 4 and member 5 at wafer-level. The second wafer isformed with the numerous spacers 6. The semiconductor wafer is formedwith the numerous lenses 4. The first wafer is formed with the numerousmembers 5. Examples of the joining method include a method in which goldto gold diffusion bonding is performed by previously forming a gold filmon each of surfaces to be joined each other, a method in which gold totin diffusion bonding is performed by previously forming a gold film anda tin film on one and other of surfaces to be joined each other,respectively, and the surface-activated bonding method.

In the infrared sensor of the embodiment, it is preferable that the lens4, the spacer 6 and the member 5 are formed integrally as mentionedabove. As a result, it is possible to enhance precision of relativepositions among the lens 4, the spacer 6 and the member 5.

FIG. 2A shows propagation paths of an infrared light (an on-axis lightand an off-axis light) that is infrared incident on the upper surface 4a of the lens 4 in a case where a distance G1 between the upper surface4 a and the member 5 of the lens 4 in the optical axis direction of thelens 4 in the infrared sensor of the embodiment is set to 0.25 mm. FIG.2B shows propagation paths of an infrared light (an on-axis light and anoff-axis light) that is infrared incident on an upper surface 4 a of alens 4 in an infrared sensor which has a similar configuration to theinfrared sensor that the upper surface 4 a of the lens 4 is in contactwith the member 5 not through a spacer 6. Propagation paths of infraredin each of FIGS. 2A and 2B were obtained by a simulation based on a raytracing method.

The example shown in FIG. 2B has a large incident angle onto the uppersurface 4 a and large off-axis aberration in a case where an incidentangle of infrared from a heat source (not shown) is large. As a result,a resolution with respect to an off-axis light (an off-axis incidentlight) from the heat source as an off-axis object point becomes low,thereby causing reduction in S/N ratio at pixels 1 b far from a centerof an infrared detecting device 1 in a case where the infrared detectingdevice 1 is an infrared sensor chip in which the pixels 1 b are arrangedin array as mentioned above. In the infrared sensor of the embodiment,the spacer 6 is provided between the lens 4 and the member 5 as shown inFIG. 2A, thereby being capable of shifting an infrared transmissionregion for an off-axis light incident on the upper surface 4 a of thelens 4 from a center to a periphery side of the lens 4, and decreasingan incident angle onto the lower surface 4 b of the lens 4. As a result,it is possible to improve a resolution for the off-axis light.

In the infrared sensor of the embodiment shown in FIG. 2A, it has beenconfirmed that off-axis aberration thereof is small in comparison withthe infrared sensor of the example shown in FIG. 2B.

In the infrared sensor of the embodiment, a thickness of the spacer 6 isset to 0.25 mm, but the numerical value is just an example and notlimited thereto. For example, the thickness of the spacer 6 may be lessthan 0.25 mm. It may be suitably designed in accordance with a lensdiameter, a back focus and the like of the lens 4.

The infrared sensor of the embodiment includes the infrared detectingdevice 1, the package 3 and the lens 4 as mentioned above, and furtherincludes the member 5 that is disposed at the side of the upper surface4 a of the lens 4 and includes the opening 5 a defining the infraredtransmission region in the lens 4, and the spacer 6 that intervenesbetween the member 5 and the lens 4. As a result, in the infrared sensorof the embodiment, it is possible to suppress the occurrence of anoff-axis aberration of the lens 4. In this embodiment, the infraredsensor includes the gap 7 between the lens 4 and the member 5, therebybeing capable of shifting an infrared transmission region with respectto an off-axis light incident on the upper surface 4 a of the lens 4from the center to the periphery side of the lens 4, and decreasing anincident angle onto the surface 4 b of the lens 4. As a result, it ispossible to improve a resolution for the off-axis light. In short, theinfrared sensor of the embodiment includes the gap 7 between the lens 4and the member 5, thereby being capable of suppressing the occurrence ofan off-axis aberration of the lens 4.

As shown in FIG. 3, the infrared sensor may include an member 5 in whichan opening 5 a is an inversely tapered opening of which area graduallyincreases in a direction apart from the lens 4. In this infrared sensor,it is possible to prevent an off-axis light from being blocked with themember 5, and to prevent the provided member 5 from narrowing adetection area and decreasing sensitivity of each pixel 1 b at theperiphery of the infrared detecting device 1. This sort of opening 5 aof the member 5 can be formed by wet etching in which an alkali solutionis used if a silicon wafer with a main surface of (100) surface isemployed as the first wafer. In this case, a taper angle of an inside ofthe opening 5 a is approximately 54.7°. In addition, the opening 5 a ofthe member 5 can be formed by using dry etching apparatus and properlysetting an etching condition thereof. If the opening 5 a of the member 5is formed by using a photolithography technique and an etching techniquealong with a gray scale mask, design freedom of each of a shape of theopening 5 a and the taper angle can be enhanced.

Preferably, the taper angle of the inside of the opening 5 a in themember 5 is equal to or less than a value obtained by subtracting, from90°, an angle that is half the size of a specified view angle. Thespecified view angle is a view angle of the infrared sensor. When thespecified view angle is 60°, the taper angle is preferably equal to orless than 60°. When the specified view angle is 120°, the taper angle ispreferably equal to or less than 30°.

Preferably, the taper angle of the inside of the opening 5 a in themember 5 is more than 0°. From view of miniaturizing the member 5 inplane size and mechanical strength of the member 5, it is preferablethat the angle be larger than a value obtained by subtracting a totalreflection angle of the upper surface 4 a from 90°.

Hereinafter, an infrared sensor of an embodiment is explained withreference to FIG. 4.

The infrared sensor of the embodiment differs from the embodiment ofFIG. 1 in that the infrared sensor of the embodiment includes aprotection portion 10 that is disposed outside the package 3 andconfigured to protect the member 5. Like kind elements are assigned thesame reference numerals as depicted in the embodiment of FIG. 1, andexplanation thereof is omitted.

For example, resin such as epoxy resin, silicone resin, polyimide or thelike may be employed as material of the protection portion 10.

The infrared sensor of the embodiment includes the protection portion 10for protecting the member 5, and it is accordingly possible to preventthe member 5 from being damaged.

Preferably, the protection portion 10 is formed on an opposite surfaceof the member 5 from the lens 4 along with an outer edge of the member5, an outer edge of the spacer 6, an outer periphery of the lens 4, andpart, around the lens 4, of the package lid 32. As a result, theinfrared sensor can protect not only the member 5 but also the spacer 6and the lens 4, thereby improving reliability thereof.

In the infrared sensor of the embodiment, the opening 5 a of the member5 is formed like the configuration of FIG. 1 as described in theembodiment of FIG. 1, but may be formed like the opening 5 a of themember 5 as shown in FIG. 3.

Hereinafter, an infrared sensor of an embodiment is explained withreference to FIG. 5.

The infrared sensor of the embodiment differs from the embodiment ofFIG. 1 in that the infrared sensor of the embodiment has a secondsurface, shaped like a convex surface, of a lens 4 as an upper surface 4a and a first surface, shaped like a plane, thereof as an lower surface4 b. That is, the lens 4 in the infrared sensor of the embodiment is thereverse of that in the embodiment of FIG. 1. Like kind elements areassigned the same reference numerals as depicted in the embodiment ofFIG. 1, and explanation thereof is omitted.

The infrared sensor of the embodiment includes an infrared detectingdevice 1, a package 3 and a lens 4 like the infrared sensor of theembodiment of FIG. 1, and further includes an member 5 that is disposedat a side of the upper surface 4 a of the lens 4 and includes an opening5 a defining an infrared transmission region in the lens 4, and a spacer6 that intervenes between the member 5 and the lens 4. The infraredsensor of the embodiment includes a gap 7 that intervenes between themember 5 and the lens 4 and has a wider range than the opening 5 a. Itis accordingly possible to suppress the occurrence of an off-axisaberration of the lens 4.

In the infrared sensor of the embodiment, the opening 5 a of the member5 is formed like the configuration of FIG. 1 as described in theembodiment of FIG. 1, but may be formed like the opening 5 a of themember 5 as shown in FIG. 3. The infrared sensor of the embodiment maybe provided with a protection portion 10 as explained in the embodimentof FIG. 4.

In each of the aforementioned embodiments, a lens 4 is disposed on anoutside of a package lid 32, but is not limited to this. The lens 4 maybe disposed on an inside of the package lid 32.

Hereinafter, an infrared sensor of an embodiment is explained withreference to FIG. 6.

The infrared sensor of the embodiment differs from the embodiment ofFIG. 1 mainly in that the infrared sensor of the embodiment includes alens 4 that is disposed so as to close a window hole 3 a of a package 3from an inside of the package 3, and part of the package 3 doubles as anmember 5. The member 5 includes the window hole 3 a as an opening 5 a.That is, the window hole 3 a doubles as the opening 5 a. Like kindelements are assigned the same reference numerals as depicted in theembodiment of FIG. 1, and explanation thereof is omitted.

A spacer 6 in the infrared sensor of the embodiment is disposed betweenthe member 5 and the lens 4 on the inside of the package 3. That is, inthe infrared sensor of the embodiment, the spacer 6 has an opening 6 alarger than the window hole 3 a and is disposed between part, around thewindow hole 3 a, of a package lid 32 (part, around the opening 5 a, ofthe member 5) and a periphery of the lens 4 (a flange portion 42 in thisembodiment). The infrared sensor includes a gap 7 that intervenesbetween the member 5 and the lens 4 on the inside of the package 3 andhas a wider range than the opening 5 a of the member 5. The spacer 6 isshaped like a frame and a whole face thereof on a side of the lens 4 isjoined to the periphery of the lens 4, and a whole face thereof on aside of the member 5 is joined to the part, around the opening 5 a, ofthe member 5. As a result, in the infrared sensor of the embodiment, aninterior space surrounded by the package 3, the lens 4 and the spacer 6can be formed as an airtight space. In the infrared sensor of theembodiment, the interior space surrounded by the package 3, the lens 4and the spacer 6 is formed as a dry nitrogen atmosphere, but not limitedto this. For example, it may be formed as a vacuum atmosphere.

The gap 7 in the infrared sensor of the embodiment is formed of a hollowspace that is shaped like a cylinder and surrounded by the member 5, thelens 4 and the spacer 6.

The opening 5 a of the member 5 is formed of the window hole 3 a of thepackage 3 and is shaped like an inversely tapered opening of which sizegradually increases in a direction apart from the lens 4. It ispreferable that a taper angle of an inside of the opening 5 a in member5 be equal to or less than a value obtained by subtracting, from 90°, anangle that is half the large of a specified view angle.

The infrared sensor of the embodiment includes the lens 4 disposed abovean infrared detecting device 1, the member 5 that is disposed at a sideof an upper surface 4 a of the lens 4 and includes the opening 5 adefining an infrared transmission region in the lens 4, and the gap 7that intervenes between the member 5 and the lens 4 and has a widerrange than the opening 5 a, like the infrared sensor of the embodimentof FIG. 1. As a result, in the infrared sensor of the embodiment, it ispossible to shift an infrared transmission region with respect to anoff-axis light incident on the upper surface 4 a of the lens 4 from acenter to a periphery side of the lens 4, and to decrease an incidentangle onto the lower surface 4 b of the lens 4, like the infrared sensorof the embodiment of FIG. 1. Accordingly, it is possible to improve aresolution for the off-axis light. Thus, the infrared sensor of theembodiment can suppress the occurrence of an off-axis aberration of thelens 4, like the infrared sensor of the embodiment of FIG. 1.

Hereinafter, an infrared sensor of an embodiment is explained withreference to FIG. 7.

The infrared sensor of the embodiment differs from the embodiment ofFIG. 6 mainly in that the infrared sensor of the embodiment includes aspacer 6 that is integrally formed in an member 5. Like kind elementsare assigned the same reference numerals as depicted in the embodimentof FIG. 6, and explanation thereof is omitted.

The member 5 includes a window hole 3 a as an opening 5 a like theembodiment of FIG. 6. In the infrared sensor of the embodiment, a recess3 b is provided in part, around the window hole 3 a, of the package lid32 which faces the upper surface 4 a of the lens 4. As a result, in theinfrared sensor of the embodiment, the spacer 6 is formed of a region,surrounding the recess 3 b, of the package lid 32. A thickness dimensionof the spacer 6 is the same as a depth dimension of the recess 3 b. Forexample, the recess 3 b can be formed by machining the package lid 32.Examples of machining include cutting and the like. The recess 3 b maybe formed when the package lid 32 is molded.

In the infrared sensor of the embodiment, since the spacer 6 isintegrally formed in the member 5, it is possible to reduce the numberof components to realize cost reduction and simplification of anassembly process. In the infrared sensor of the embodiment, the spacer 6is integrally formed in the member 5, and it is thereby possible toincrease the precision of relative positions among the lens 4, thespacer 6 and the member 5 and to further suppress an occurrence ofoff-axis aberration.

In the infrared sensor of the embodiment, the opening 5 a of the member5 has an opening shape of which opening area is uniform regardless ofdistances from the lens 4 in an optical axis direction of the lens 4,but is not limited to this. It may have an inversely tapered openingshape of which opening area gradually increases in a direction apartfrom the lens 4.

In the infrared sensor of the embodiment, the spacer 6 is formed byproviding the recess 3 b in the part, around the window hole 3 a, of thepackage lid 32, but not limited to this. It may be formed by integrallyforming a protrusion as the spacer 6 on part, around the window hole 3a, of the package lid 32.

Hereinafter, an infrared sensor of an embodiment is explained withreference to FIG. 8.

The infrared sensor of the embodiment differs from the embodiment ofFIG. 6 mainly in that the infrared sensor of the embodiment includes aspacer 6 that is integrally formed in a lens 4. Like kind elements areassigned the same reference numerals as depicted in the embodiment ofFIG. 4, and explanation thereof is omitted.

In the infrared sensor of the embodiment, a recess 4 c is provided in asurface side of the lens 4 that faces a package lid 32 in an opticalaxis thereof. As a result, in the infrared sensor of the embodiment, thespacer 6 is formed of a region, surrounding the recess 4 c, of the lens4. A thickness dimension of the spacer 6 is the same as a depthdimension of the recess 4 c. In the lens 4, an inner bottom of therecess 4 c can be an upper surface 4 a. In a case where an opticalfilter film is provided on each side of the upper surface 4 a and anlower surface 4 b of the lens 4, optical properties of the two opticalfilter films may be the same as or different from each other.Alternatively, one side of the upper surface 4 a and the lower surface 4b of the lens 4 may be provided with an optical filter film, while theother side thereof may be provided with an antireflection film forpreventing infrared reflection. The antireflection film may be formed ofmaterial similar to the optical filter film, and laminate structurethereof can be designed suitably.

For example, the lens 4 can be formed by a manufacturing method forsemiconductor lens adopting the aforementioned anodic oxidationtechnology. That is, it is preferable that the lens 4 be formed of asemiconductor lens (e.g., a silicon lens or the like). In amanufacturing example of the semiconductor lens, a semiconductorsubstrate (e.g., a silicon substrate or the like) is prepared. An anodeby designing a contact pattern with the semiconductor substrate inaccordance with a shape of a desired lens is then formed on a firstsurface side of the semiconductor substrate so as to form ohmic contactas contact with the semiconductor substrate. A second surface side ofthe semiconductor substrate is anodized in an electrolytic solutioncontaining a solution for removing, by etching, oxide of constituentelement of the semiconductor substrate, thereby forming a porous regionto be removed. The porous region is then removed, so that asemiconductor lens is formed. Preferably, the spacer 6 formed of therecess 4 c and part around the recess 4 c is then formed by etching aforming region of a recess 4 c from the first surface side of thesemiconductor substrate after the anode on the first surface side of thesemiconductor substrate is removed. An optical film such as theaforementioned optical filter film, the antireflection film or the likemay be then formed as needed. For example, the aforementioned lens 4 maybe obtained by employing a semiconductor wafer (e.g., a silicon wafer)as the semiconductor substrate to form numerous lenses 4 and thenseparating into individual lenses 4 by dicing or the like.

Examples of etching for forming the aforementioned recess 4 c includedry etching and wet etching using a drug solution. Preferably, the wetetching is anisotropic etching dependent on orientation of crystalplane. In a case where a silicon substrate in which the aforementionedsecond surface is (110) plane or (100) plane is employed as thesemiconductor substrate, it is preferable that the wet etching beanisotropic etching dependent on orientation of crystal plane using analkali solution that is a TMAH (tetra-methyl ammonium hydroxide)solution, a KOH solution or the like.

In the infrared sensor of the embodiment, since the spacer 6 isintegrally formed in the lens 4, it is possible to reduce the number ofcomponents to realize cost reduction and simplification of an assemblyprocess. In the infrared sensor of the embodiment, the spacer 6 isintegrally formed in the lens 4, and it is thereby possible to increasethe precision of relative positions among the lens 4, the spacer 6 andthe member 5 and to further suppress an occurrence of off-axisaberration.

In the infrared sensor of the embodiment, the opening 5 a of the member5 has an opening shape of which opening area is uniform regardless ofdistances from the lens 4 in an optical axis direction of the lens 4,but is not limited to this. It may have an inversely tapered openingshape of which opening area gradually increases in a direction apartfrom the lens 4.

Each infrared sensor of the aforementioned embodiments includes an ICdevice 2 and a cover member 8 inside a package 3, but may be aconfiguration without the IC device 2 and the cover member 8. And, themember 5 may not integrally formed with the spacer 6. Therefore, acomposition of the member 5 may be different from a composition of thespacer 6. For example, when the member 5 is made of silicon and thespacer 6 is made of silicon, the composition ratio of silicon may bedifferent from each other.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that they may be appliedin numerous applications, only some of which have been described herein.It is intended by the following claims to claim any and allmodifications and variations that fall within the true scope of thepresent teachings.

The invention claimed is:
 1. An infrared sensor, comprising: an infrareddetecting device; a lens disposed above the infrared detecting device; amember that is disposed on an upper surface of the lens and includes anopening; a gap that is disposed between the member and the lens and hasa wider range than the opening; and a package that houses the infrareddetecting device, wherein the package includes a window hole disposedabove the infrared detecting device, and the lens is disposed so as toclose the window hole.
 2. The infrared sensor of claim 1, wherein awidth of the window hole is larger than a width of the gap.
 3. Aninfrared sensor, comprising: an infrared detecting device; a lensdisposed above the infrared detecting device; a member that is disposedon an upper surface of the lens and includes an opening; a gap that isdisposed between the member and the lens and has a wider range than theopening; a cover member disposed above the infrared detecting device;and a package that houses the infrared detecting device and the covermember, wherein the upper surface of the lens is positioned upper thanan upper surface of the package.
 4. The infrared sensor of claim 3,wherein the package has a window hole, and a side surface of the lens isapart from the package.